Beneficial uses of microorganisms are well known in the art and have been documented at great length. Many patents have issued which claim new microbial processes pertaining to the production of antibiotics, enzymes, ethanol, and a multitude of other useful products. Microorganisms are also used to clean up toxic wastes and oil spills, kill pests, recover minerals, and provide nutrients to plants. It has been known for many years that some organisms produce compounds which are toxic to other organisms. The production of the antimicrobial compound penicillin by penicillium mold is one such example.
Microorganisms are particularly attractive candidates for use in making and delivering organic compounds because they can be extremely efficient and safe. The modern tools of genetic engineering have greatly enhanced the ability to exploit the efficiency and relative safety of microbes. Even in the absence of genetic manipulation, however, microbes can perform highly specific tasks which make them indispensable in certain applications. Thus, there is a constant ongoing search in many areas of research for previously unknown microbes with specific advantageous properties. The subject invention concerns the discovery of such microbes.
Weeds are a tremendous problem for farmers throughout the world. Weeds cause a 10-12% loss of value for agricultural products in the United States, the most recent estimate being $20 billion annually (McWhorter, C. G. [1984] Weed Sci. 32:850-855).
Undesirable grasses are a significant problem to homeowners, golf courses, and agriculture workers. Chemical control of these grasses may pollute the environment and often does not provide the necessary selectivity to kill pest grasses without harming desirable vegetation.
There exist multiple societal pressures for the replacement of chemical pesticides with alternate control methods. One area of active research along these lines involves the use of plant pathogens which can attack weeds. Although the existence of these pathogens is well known, and some of these pathogens have been patented, there are very few commercial products utilizing bioherbicides and these enjoy only limited use. For the most part, the organisms employed have been fungal pathogens with a much more limited effort having been directed towards bacterial pathogens. The process for finding such "bioherbicide" pathogens has a low success rate for yielding commercially applicable discoveries.
Microorganisms can be associated with plants in many ways. For example, some are saprophytic and some are pathogenic, but even those which are pathogens may exist only rarely in a phase of their life cycle or epidemiological event in which signs or symptoms of disease are evident. Many organisms which can be pathogenic under certain circumstances exist as epiphytes or endophytes on or in plants which are "healthy". These associations have been documented in the literature.
Some bacteria are known to infect certain grasses causing the grasses to be suppressed or killed. These infections have been known in various geographic locations as important problems for the maintenance of desirable grasses. A bacterial infection of Toronto creeping bentgrass which is used on golf putting greens is described by Roberts, D. L., et al. in Plant Disease 65, 1014-1015 (1981); Roberts, D. L., et al., Plant Disease 66, 804-806 (1982); Roberts, D. L., et al., Scanning Electronic Microscopy IV, 1719-1722 (1983). The bacterium was identified as a Xanthomonas campestris by Roberts, D. L. in Phytopathology 73, 810 and 74, 813 (1984). The solution to the problem was treatment of the infection with oxytetracycline, an antibiotic. A disease of Poa annua L. was also described by Roberts, D. L. in Phytopathology 75 1289 (1985). The organism causing this disease has been deposited as NRRL B-18018 and is designated herein as MB218. In their 1982 paper, Egli and Schmidt described three new pathovars of Xanthomonas campestris which caused wilt diseases of forage grasses. Previously all such wilt organisms were classified as X. campestris p.v. graminis, but by studying a large collection of isolates, these workers found some isolates with much narrower host ranges than the typical, graminis pathogens. One of these, p.v. poae, (ATCC 33804; MB238) was shown to cause wilting in only a few species of the genus Poa, most notably Poa trivialis or rough bluegrass.